1. Technical Field
The present invention relates to electrophotographic printers in general, and, in particular, to an apparatus for improving image fidelity on electrophotographic printers. Still more particularly, the present invention relates to an apparatus for providing delay signals to perform print scan line synchronization within a laser printer.
2. Description of Related Art
Laser printers are designed to produce an image on paper or other print material at virtual positions defined by a digital raster. These virtual positions in the raster are known as “pixels.” In laser printers, the image is typically first produced on a charged photoconductive material by scanning the photoconductor with a laser beam in a sequence of scan lines. A laser printer may scan the surface of the photoconductive material with a laser in the sequence of scan lines using a rotating polygonal mirror. As a line is being scanned, or written, the laser beam is energized during the extent of each pixel. When the laser beam is energized, the portion of the photoconductor upon which the laser energy impinges is discharged, thereby producing a charge-pattern copy of the desired image on the photoconductor. The printed output is obtained by attracting toner to the charge-pattern and by transferring the developed image to paper or other types of print material.
If the laser beam is modulated, then variations in charge are translated to proportionate amounts of toner deposited on a sheet of paper in the printer. The laser scans the photoreceptor surface to generate a signal at the beginning of each scan line that is used to initiate modulation of the laser beam for that scan line. Such signal is called a beam detect signal, and is asynchronous to the input clock reference oscillator. The clock reference oscillator determines the width of each printed pixel.
The present disclosure provides an apparatus for providing delay signals to perform print scan line synchronization within a laser printer.